The present invention relates to an immune-modulating peptide. The formyl peptide receptor family (formyl peptide receptor (FPR) and formyl peptide receptor-like 1 (FPRL1)) that is expressed in phagocytic cells such as neutrophils and monocytes plays an important role in host defense against pathogen infection (1, 2). The receptors have been known to couple with pertussis toxin-sensitive Gi proteins (1, 2). Activation of FPR induces dissociation of Gβγ subunits from Gαi subunits, and the βγ-subunits mediate the activation of phospholipase Cβ or phosphoinositide 3-kinase (1, 2). Activation of these effect molecules induces complicated downstream signaling leading to diverse cellular responses such as chemotactic migration, degranulation, and superoxide generation.
Most full agonists induce a lot of complicated cellular signaling that evokes eventual complex immune responses. Among the immune responses, many of them are essentially required for the proper functioning of host cells to clear out invading pathogens, but some responses are unwanted side effects in immune responses. In the area of drug development, it has been a hot issue to reduce or remove the side effects of drug candidates. To obtain this objective, many research groups have tried to develop selective immune response modulators or selective antagonists for specific receptors via several approaches (3, 4).
A variety of agonists for FPR have been identified from endogenous sources or artificial synthesis (1, 2). They include bacterial peptides (N-formyl-methionyl-leucyl-phenylalanine (fMLF)), HIV-envelope domains (T20 and T21), and host-derived agonists (Annexin I and Aβ42) (5-7). Previously, the inventors of the present invention reported a synthetic peptide ligand, Trp-Lys-Tyr-Met-Val-D-Met-NH2 (hereinafter, referred to as “WKYMVm”; SEQ ID NO: 25) that stimulates leukocytic cells such as monocytes and neutrophils (8-11). Le et al. demonstrated that WKYMVm (SEQ ID NO: 25) binds to formyl peptide receptor (FPR) and formyl peptide receptor-like 1 (FPRL1) (12). Since WKYMVm (SEQ ID NO: 25) is a short peptide with a high affinity for a broad spectrum of receptors, it can be a useful material for the study of FPR- or FPRL1-mediated signaling. However, research to develop selective immuno-modulators or selective antagonists for specific receptors, as well as screening of molecular diversity, consists of small compounds and thus far has been very limited, and therefore there are continuing demands for identifying novel compounds.